1. Field of the Invention
The invention is directed to an improved fuel injection system for an internal combustion engine.
2. Description of the Prior Art
One fuel injection system known from German Patent Disclosure DE 198 53 103 A1 has a feed pump by which fuel is pumped to a high-pressure pump, and the high-pressure pump pumps fuel at high pressure into a reservoir. A fuel metering device is also provided, which is disposed between the feed pump and the high-pressure pump. The fuel metering device serves to control the fuel quantity, pumped into the reservoir by the high-pressure pump, as a function of engine operating parameters. The fuel metering device includes an actuator in the form of an electromagnet and a regulating valve, actuated by the electromagnet, that has a slidelike valve member which is movable counter to a restoring spring by an armature of the electromagnet. In cooperation with an outflow opening of the valve housing, via its outer jacket, the valve member controls a flow cross section from the feed pump to the high-pressure pump as a function of its stroke. In a closing position of the valve member, the valve member has its outer jacket overlapping with the outlet opening, so that the flow cross section is completely closed. However, since the valve member must be displaceable in the cylinder bore of the valve housing, a slight gap must be present between its outer jacket and the cylinder bore, through which a leakage quantity of fuel can pass and reach the outlet opening to the high-pressure pump, even when no fuel is to be pumped by the high-pressure pump because of the engine operating parameters, for instance in the overrunning mode. Provisions are therefore required to carry this leakage quantity of fuel away so that it cannot reach the high-pressure pump. To that end, a bypass connection from the outlet of the feed pump to the fuel tank is provided, in which there is a throttle restriction. This makes the layout and manufacture of the fuel injection system complicated.